Name:	met_MaximumPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The upper range performance factor range used to determine final number of performance units payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MaximumPerformanceFactorForPerformanceUnits
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The lower range performance factor range used to determine final number of performance shares payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MinimumPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The lower range performance factor range used to determine final number of performance units payable being determined by the product of the initial target multiplied by this performance factor that is applied based on measurement of the Company's performance.

No definition available.

Name:	met_MinimumPerformanceFactorForPerformanceUnits
Namespace Prefix:	met_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

The percentage of the performance factor for the three year performance period.

No definition available.

Name:	met_PerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

As of the balance sheet date, the number of shares expected for pay out based on the performance factor.

No definition available.

Name:	met_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedNumberOfSharesBasedOnPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

As of the balance sheet date, the number of units expected for pay out based on the performance factor.

No definition available.

Name:	met_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsExpectedNumberOfUnitsBasedOnPerformanceFactor
Namespace Prefix:	met_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod
Namespace Prefix:	us-gaap_
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(d)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901